Apparent boudinage in dykes


Contact
paul.bons [ at ] uni-tuebingen.de

Abstract

Intrusive rocks may be arranged in the form of strings of lenses or beads, as found on the Cap de Creus Peninsula, NE Spain, and in the South Finland MigmatiteGranite Belt. These structures first appear to be the result of stretching and boudinage of intrusive sheets or dykes. However, closer examination reveals that they are not boudins, but are instead primary intrusive structures. A detailed study was performed on a swarm of pegmatite intrusions at Cap de Creus. Layering is often continuous between beads, and, in some cases, individual beads exhibit a very irregular shape. These observations are shown to be incompatible with an origin by boudinage. Analogue experiments were used to test the effect of the two models (boudinage and emplacement) on the structures around beads, and show that an emplacement model of local expansion and collapse of magmatic sheets is the most compatible with field observations. Such structures can only form when dykes intrude hot rocks, when magma solidifies slowly enough to allow enough ductile flow of the wall rock to accommodate the formation of the beads. The fact that the pegmatite bead strings are not boudins has repercussions for the interpretation of the deformation at Cap de Creus and necessitates caution in the interpretation of deformation based on apparent boudins in intrusive rocks in other areas.



Item Type
Article
Authors
Divisions
Programs
Publication Status
Published
Eprint ID
10251
Cite as
Paul D. Bons, E. D. (2004): Apparent boudinage in dykes , Journal of structural geology, 26 , pp. 625-636 .


Share
Add to AnyAdd to TwitterAdd to FacebookAdd to LinkedinAdd to PinterestAdd to Email

Research Platforms
N/A

Campaigns
N/A


Actions
Edit Item Edit Item